Effects of work surface height on muscle activity and posture of the upper extremity during simulated pipetting

Pipetting is the task of transferring small exact amounts of liquid from one vessel to another using a pipette, a very narrow cylinder with a valve usually operated by the thumb. A pipette operation usually consists of tipping, aspirating, dispensing and tip ejection.

The pipette operation, which is performed either standing or seated, involves repetitive activities in combination with muscle strain and/or awkward postures of the upper extremity (UE). Ergonomic risk factors in pipette work have been documented by a number of researchers.

In order to examine the effects of work surface height (WSH) on muscle activity, posture and discomfort during simulated pipetting, the authors did an experimental study which was conducted using electromyography, electrogoniometry, video techniques and also qualitative data. The experimental design consisted of one independent variable (WSH with six heights) and 13 dependent variables. The levels of muscle strain and discomfort were significantly lower at the shoulder when the WSHs were low but thumb muscle activities and neck flexion levels were markedly higher at these WSHs compared to higher WSHs.

To reduce shoulder strain, without raising thumb and neck strain beyond acceptable limits, the findings suggest that the height of a laboratory workbench should be at the level of the pipette tip when held in a standing position with the hand at elbow height.

It was also found that pipetting should not be done in a seated posture.

The authors suggested that the laboratory workbench height should be at the pipette-tip level when held in a standing position with the hand at elbow height.